A nonlinear viscoelastic constitutive model with damage and experimental validation for composite solid propellant

Abstract

The development of a nonlinear viscoelastic constitutive model of composite solid propellant (CSP) coupled with effects of strain rate and confining pressure is essential to assess the reliability of solid propellant grains during ignition operation process. In the present work, a nonlinear viscoelastic constitutive model with novel energy-based damage initiation criterion and evolution model was firstly proposed to describe the coupled effects of confining pressure and strain rate on mechanical responses of CSP. In the developed damage initiation criterion and evolution model, the linear viscoelastic strain energy density was introduced as the damage driving force, and the coupled effects of strain rate, damage history and confining pressure on damage growth were taken into account. Then, uniaxial tensile tests from low strain rates to medium strain rates and various confining pressures, and stress relaxation tests were conducted using a self-made active confining pressure device. Finally, the identification procedures of model parameters and validation results of the constitutive model were presented. Moreover, the master curve of damage initiation parameter was constructed through the time-pressure superposition principle (TPSP). The results show that the developed nonlinear constitutive model is capable of predicting the stress–strain responses of CSP under different strain rates and confining pressures.

Modeling of AP-HTPB Solid Propellant Viscoelastic Behavior Using Modified Maxwell Model

“…Additionally, the comparison between the simulated results and experimental data was limited to the summation of reaction forces for the initial 30 seconds, omitting the in uence of diverse loading conditions and temperature variations. Hui Li and Jin-sheng Xu [21] used the Prony series called by the generalized Maxwell model to compare the model results of relaxation modulus with the experimental results of the CSP at room temperature, the next step is to compare the experimental data with Ansys's calculation of the reaction forces for the rst 30 seconds, without changing the temperatures or loading conditions. A relaxation test can be used to determine the relaxation modulus, which is important for SRM design because propellants with higher relaxation moduli will cause surface cracks during actual ring, while propellants with lower relaxation moduli will cause grain deformation during storage [9][10][11][12][13][14][15][16][17][18].…”